Nghiên cứu ứng dụng kỹ thuật chiếu sáng LED (light emitting diodes) sản xuất rau ăn lá trong nhà tt tiếng anh

1.3 New contributions of the thesis - The thesis had identified: + LED had 80% red: 20% blue spectrum was approriate for growth, yield of baby radish greens, mustard greesn and mature l

MINISTRY OF EDUCATION AND TRAINING

CAN THO UNIVERSITY

SUMMARY MAJOR: CROP SCIENCE Code: 62 62 01 10

PHAN NGOC NHI

STUDY OF LED (Light-Emitting Diodes) LIGHTING TECHNOLOGY APPLICATION TO PRODUCE

LEAFY VEGETABLES INDOOR

Can Tho, 2020

WORRK DONE IN CAN THO UNIVERSITY

Instructor 1: Assoc Prof Dr Tran Thi Ba

Thesis seminar at: Dortoral Dissertation Defe, Can Tho University Time:

LIST OF PUBLISHING

1 Phan Ngoc Nhi, Nguyen Thi Kieu Khuyen, Tran Thanh Hau, Vo Thi Bich

Thuy and Tran Thi Ba, 2018 Effects of LED light spectrum on growth and yield of hydroponic lettuce Science and Technology Journal of Agriculture

& Rural Development Ministry of Agriculture and Rural Development, Viet Nam (ISSN 1859-4581), Special issue 8/2018: 199-205

2 Phan Ngoc Nhi, Tran Thi Ba, Vo Thi Bich Thuy, Nguyen Binh Khang,

Bui Thi Cam Thu and Ho Thi Cam Nhung, 2019 Effects of LED light intensities and photoperiod regimes on growth and yield of baby golden frills

mustard greens (Brassica juncea L.) Journal of Vietnam Agricultural

Science and Technology (ISSN 1859-1558), 2 (2019): 54-59

3 Phan Ngoc Nhi, Tran Thi Ba, Vo Thi Bich Thuy, Mai Phuc Thanh,

Nguyen Phuong Uyen and Nguyen Thi Anh Thu, 2019 Effects of photoperiod regimes supplemental LED lighting on growth and yield of

lettuce (Lactuca sativa L.) under multilayer hydroponic cultivation in

greenhouse Journal of Vietnam Agricultural Science and Technology (ISSN 1859-1558), 5 (2019): 43-48

Chapter 1: INTRODUCTION 1.1 The urgency of the topic

Since 2007, more than 50% of the world's population has lived in urbaning areas and it was estimated that by 2050, this number will rate more than 70% Therefore, more and more people were starting to tend about urban agricultural production (Despommier, 2010) Urban agriculture has two basic benefits that help people in the city to conduct farming as a hobby, an entertaining activity in their daily and create safe food sources for families as well or more which provided to nearby residents (Kozai, 2016) Facing these facts, many people in the city have taken in advanced the terrace or balcony to grow vegetables However, a small area

of planting and lack of sunlight has caused many difficulties for growers

LEDs are considered as an optimal artificial light source in replacing sunlight

for photosynthetic (Shimizu et al., 2011) LED lamps have many advantages such

as low power consumption, small size, long lifespan and lower releasing heat than

fluorescent lamps and high-pressure lamps (Gupta and Jatothu, 2013, Tewolde et al.,

2016) More importantly, the light-emitting diode technology (LED) is abled to produce the appropriate blue and red monochromatic wavelengths for maximum absorption of chlorophyll a and chlorophyll b in plant photosynthesis (Shimokawa

et al., 2014) In Vietnam, the research and application of artificial LED lighting in

agricultural production are progressively focused However, there have not been many LED studies that applied on vegetables, especially leafy vegetables Therefore,

it is extremely necessary to conduct this study nowadays

1.3 New contributions of the thesis

- The thesis had identified:

+ LED had 80% red: 20% blue (spectrum) was approriate for growth, yield

of baby radish greens, mustard greesn and mature lettuce

+ When used 80% red: 20% blue LED with intensity of 107 μmol.m s and lighting of 20 hours/day, the growth and yield of baby radish greens, mustard greens and mature lettuce were affectively better than other treatments

+ With multi-tiers growing shelf in greenhouse, baby radish greens, mustard greesn and mature lettuce were added 80% red: 20% blue LED with intensity of 107 μmol.m-2.s-1 in 16 hours/day so that gave the best efficiency

- The thesis also showed the outstanding advantages of applying LED light

in multi-tiers growing shelf of vegetable production compared to traditional way It was obviously a premise to build up and develop models of LED lamps for vegetable growing in commercial production

1.4 The scientific and practical significance of the thesis

- The thesis has contributed the results of basic research on LED light application in farming The scientific basis diversity for future was opened in order

to approach the trendy indoor vegetable farming development in advanced agricultural countries

- This result can be also incorporated the curriculum and reference materials for further studies on the effect of artificial light for some leafy vegetables

- Demanding self-production for some leafy vegetables in urban regions and big cities where are lack of farming space and natural light condition

- Contributing an important part in building up the production process for baby greens and mature lettuce under multi-tiers growing shelf to increase vegetable production per unit area

- It is a necessary foundation for appling LED in multi-tiers growing shelf vegetable production towards commercial production

Chapter 2 LITERATURE REVIEW 2.1.1 Overview of indoor plants production

The term "plant factory" is used primarily in Asia, to describe an agricultural production base that operates as a typical industrial production facility These facilities are carefully designed, full of areas corresponding to each stage of plant development Internal environmental conditions in production facilities such as temperature, humidity, light, CO2 concentration and standards of nutrient solutions are always controlled according to requirements Facilities are also equipped with sensor systems that control the process of automating certain stages in the factory

(Ting et al., 2016)

Fluorescent lamps, high-pressure sodium lamps and LEDs are often used as

single lighting sources or mixed lighting sources for crop plants (Zhang et al., 2015)

In recent years, LED lamps have been the best choice in existing artificial light sources LEDs are able to reduce the cost of power consumption by converting energy efficiently to suitable light wavelengths for plants, while reducing cooling costs for manufacturing plants by the amount of heat emission is lower than other artificial light sources Besides, compact LED design is suitable for installation according to multi-stages plant design However, the high initial investment cost is currently a major obstacle to the development of LED applications in agricultural

production (Ting et al., 2016)

2.2.2 Effect of light on plant morphogenesis

According to Higuchi and Hisamatsu (2016), light was not only used for plant photosynthesis, but also a signal that regulates growth and development throughout their life cycle When the quality, the intensity and the time of lighting changes, it will lead to changes in the morphology of plants It can be seen through by the changing in the structure and shape of plants such as seed germination, flower initiation, leaf size expansion, avoiding neighboring plants, extending the body and synthesizing pigments Light signals are received by photoreceptors, affecting the circadian rhythms and directly activating the light response

Different wavelengths of light influence each stage of plant growth The photosynthesis system reacted most clearly to red light (wavelength 600-680 nm) and blue light (wavelength 380- 480 nm) (Roberto, 2003) Therefore, when studying the effect of LED wavelengths on crop growth and productivity, most authors used red and blue light wavelengths

2.2.3.1 Blue light

Blue light had a wavelength of 400-500 nm, capable of inhibiting the stem elongation of many crops (Cosgrove, 1981) The combination with red light was essential for plants to be not excessively prolonged (Randall and Lopez, 2014) Blue light with or without red light can affect the density and aperture of stomata However, when adding a certain amount of blue light to red light, the aperture of the stomata increased significantly compared to the monochromatic red light The increase in stomata opening increases CO2 uptake leading to increased

photosynthetic activity (Kinoshita et al., 2001)

The requirement for blue light is necessary for the normal development of plants that vary by species The plant's response to blue light was first introduced by

Wheeler et al., (1991), at the same time proved a link of the length of soy stalks with

a blue light content In addition, with a blue light intensity of about 30 μmol.m-2.s-1,

it prevents stem growth and elongates slang Similar results were found by Yorio et

al (1998), on wheat, potatoes, soybeans, lettuce and cabbage objects to ensure

normal growth and development, the minimum blue light intensity of 30 μmol.m-2.s

-1 was required

The 450 nm light spectrum allows cryptochrome and phototropin to react in plants Cryptochrome changes the circadian rhythm (changing from the respiratory cycle to the photosynthetic cycle) The protein phototropin stimulates plants to open stomata, bending towards light to help develop stems and form chlorophyll Blue light wavelength also stimulates plant growth through strong root formation and high intensity photosynthesis This spectrum of light is used in the period of seedling, sapling and growth If you want the plant to stop growing, this wavelength must be reduced or eliminated (Cosgrove, 1981)

2.2.3.2 Red light

Red light has a wavelength of about 600-700 nm One of the most common roles of red light is to participate in the vital physiological activity of photosynthesis Specifically, the red light of the LED is at a wavelength of 660 nm, very close to the absorption peak of chlorophyll (Massa et al., 2008) Therefore, the red of LEDs are used to promote photosynthetic performance, resulting in increasing biomass and total yield However, the monochromatic red light is not enough to make the crop achieve optimum yield and quality Under the condition that only monochromatic red light is present, the eucalyptus axis in many dicotyledons extends excessively

(Hoenecke et al., 1992) But when combined with blue light (400-500 nm) it is

possible to control the elongation of the stem, petiole and prevent other

morphological abnormalities when only using red light alone (Goins et al., 1998,

Kigel and Cosgrove, 1991)

The red light is the most important wavelength for photosynthesis, flowering and fruit setting It is used to extend the light cycle, stimulate flowering plants for long-day plants (dragon fruit, gladiolus, etc.) or prevent flowering in short-day plants (chrysanthemum ) Especially with red light emitted from high pressure sodium lamp is very good for flowering and fruit formation (Roberto, 2003) In order to create optimal conditions for plant growth, chossing the right light source for light intensity, lighting time and light color is the decisive factor (Roberto, 2003 and

Sirtatutas et al., 2014)

In some plants such as lettuce, tobacco, light is an important factor affecting seed germination process According to Borthwick et al (1952) demonstrated that red light (600-700 nm) promotes the germination of most lettuce varieties, while red light (700-800 nm) is the opposite Phytochrome is the main place to receive light affecting the germination process Classical physiology has hypothesized that there is a link between the gibberellin (GA) and abscisic acid (ABA) hormones within plants with seed germination The red light promotes seed germination by possible addition of GA to the seed In contrast, ABA supplementation will prevent germination Thus, the endogenous content of GA and ABA can be adjusted by light In fact, GA and ABA endogenous content are inverted

in bright conditions Phytochrome regulates GA biosynthesis during germination ABA accumulation in the seeds triggers dormancy and prevents germination

Chapter 3 MATERIALS AND METHODS 3.1.1 Time and location: from May 2016 to January 2019 at the Fresh Vegetable

Research Greenhouse, College ofAgriculture, Can Tho University

3.1.2 Materials: Various types of LEDs with different wavelengths were provided

by Rang Dong Thermos Bulb Joint Stock Company GN 63 lettuce variety was provided by Nguyen Nong Company Limited (Gino) The radish greens and mustard greens varieties were supplied by Trang Nong Trading Company Limited

(b)

(c)

(a) (d)

Figure 3.1 LEDs with different spectra were

used in this study (a) LED light bar, (b) red

LED, (c) blue LED and (d) 50% red: 50%

blue LED

Figure 3.2b 4-tiers shelf with

LED light

3.2 Study content: 4 contents with 8 experiments (Ex), (4 experiments on baby

greens and 4 experiments on mature lettuce) (Fig 3.5)

Figure 3.5 Step-conducting Diagram of the thesis

3.3 Study methods

(1) Effect of LED spectrum: the experiments were arranged in a completely

random with 4 replications on baby radish greens and mustard greens and 8

replications on mature lettuce Eight treatments included 7 types of LED spectrum and natural light: (1) red LED (660 nm), (2) blue LED (450 nm), (3) white LED, (4) 50% red: 50% blue LED, (5) 60% red 40% blue LED, (6) 70% red: 30% blue LED, (7) 80% red: 20% blue LED and (8) natural light (control)

Ex 7 Baby radish

and mustard greens

Ex 8 Mature lettuce

(a) (b) (c) (d)

Figure 3.6 Treatments of LED spectrum and natural light (a) red LED, (b) blue

LED, (c) white LED, (d) 50% red:50% blue LED, (e) 60% red:40% blue LED, (f) 70% red:30% blue LED, (g) 80% red:20% blue LED and (h) natural light

(2) Effect of LED light intensities and photoperiods: the experiments were in a

completely randomized design with 2 factors and 5 replications Factor A consisted

of 6 photoperiod regimes: 14/10, 16/8, 18/6, 20/4, 22/2 and 24/0 (light/dark) Factor

B consisted of 4 levels of light intensity: 40, 66, 107 and 137 μmol.m-2.s-1 in corresponding with 1, 2, 3 and 4 bars of 80% red: 20% blue LEDs (chosen from content 1)

Figure 3.7 b Baby greens under 3-tiers

shelf

Figure 3.8 Overview of the

experimental layout of the

supplementary LED lighting

(3) Effect of supplemental LED lighting periods under 3-tier growing shelf in greenhouse: the experiments were completely randomized design with 6 treatments

and 7 replications on baby radish greens and mustard greens and 9 replications on mature lettuce Treatments included: (1) 10 hours, (2) 12 hours, (3) 14 hours, (4) 16

hours, (5) 18 hours and (6) 20 hours of supplemental LED lighting (80% red: 20%

blue LEDs, light intensity of 107 μmol.m-2.s-1- chosen from content 2)

(4) Effect of indoor growing models using LED lights with traditional way: the experiments were in a completely randomized design which consisting of 3 treatments and 7-9 replications Experiments included: Planting on hydroponic shelves (3 tiers) using LED (3-tiers hydroponic shelf + LED), planting hydroponics

in greenhouses (Hydroponics + Natural light), planting in the open field (Open field condition)

3.4 Monitoring indicators

- Plant height (cm): Using ruler to measure from the surface of the substrate

to the highest leaf tip

- Number of leaves (leaves/plant): count all true leaves with 0.5 cm of length

in order to compare the mean values at confidence of 95%

Chapter 4: RESULTS AND DISCUSSION 4.1 Effect of LED spectrum

4.1.1 Baby radish and mustard greens

a The height of plants

Baby radish greens under red LED treatment always gave the highest plant height (11.8-23.8 cm at 7-19 DAS), then combination of red and blue LED treatments Otherwise, blue LED and white LED treatment always resulted the lowest height of baby radish greens (Table 4.1)

The increasing effect of red LED light on the plant height was also shown

on baby mustard greens, in this treatment, the height was always highest (7.35-16.6

cm, respectively at 7-19 DAS) and no significant difference compared with 80% red:

20% blue LED and natural light at 19 DAS (16.8 and 16.7 cm, respectively) Obviously, the height of baby mustard greens tendentiously derease and is inversely proportional to the increase in the rate of blue LED in this study (Table 4.2)

Table 4.1 The height of baby radish greens effected by LED light spectrum at

different days affter sowing

LED light spectrum Plant height (cm) at different DAS

7 11 15 19 Red LED 11.8a 18.5a 19.8a 23.8a

Blue LED 9.53d 13.6c 18.3c 20.1f

White LED 8.63e 13.8c 18.9b 20.4ef

50% red:50% blue LED 9.53d 14.8b 20.0a 21.3cd

60% red:60% blue LED 9.53d 14.9b 18.9b 20.8de

70% red:30% blue LED 9.95c 15.4b 19.0b 21.5c

80% red:20% blue LED 10.7b 13.6c 20.1a 22.9b

Natural light - Control 7.60f 12.7d 17.8d 20.9de

CV (%) 2.45 2.79 1.42 1.85

The values in each column followed by different characters are significantly different (Duncan test, P < 0.05).**: Significant at P ≤ 0.01

Table 4.2 The height of baby mustard greens effected by LED light spectrum at

different days affter sowing

LED light spectrum Plant height (cm) at different DAS

7 11 15 19 Red LED 7.35a 11.0a 15.3a 16.6a

Blue LED 6.45b 9.33bc 11.4d 14.2d

White LED 6.10c 9.28c 10.5e 13.1e

50% red:50% blue LED 6.40b 9.33bc 10.6e 14.9c

60% red:60% blue LED 6.45b 9.35bc 13.3c 14.8c

70% red:30% blue LED 6.53b 9.45bc 13.1c 15.5b

80% red:20% blue LED 6.55b 9.48bc 13.9b 16.8a

Natural light - Control 6.50b 9.52b 13.8b 16.7a

Zhang et al (2017), Shimokawa et al (2014) and Samuoliene et al (2010) This

could be explained by the fact that under monochromatic red condition, the

eucalyptus axis in many dicotyledons extended excessively (Hoenecke et al., 1992)

Howerver, it possibly prevented the stem elongation when combined with blue light

(Goins et al., 1998, Hoenecke et al., 1992, Kigel and Cosgrove, 1991)

b Number of leaves

Baby radish greens under the combination of red and blue LED treatments always rated the highest result (1.63-1.68 leaves/plant and 3.08-3.20 leaves/plant, respectively at 11 and 19 DAS) and was insignificant difference from control treatment - natural light (1.58 and 3.20 leaves/plant, respectively at 11 and 19 DAS) The lowest number of leaves was found under white LED light (Table 4.3)

Table 4.3 The number of leaves on baby radish greens affected by the LED spectrum

50% red:50% blue LED 1.68a 2.05ab 3.13a

60% red:60% blue LED 1.63a 2.05ab 3.10a

70% red:30% blue LED 1.65a 2.20a 3.08a

80% red:20% blue LED 1.63a 2.20a 3.20a

Natural light - Control 1.58a 2.22a 3.20a

50% red:50% blue LED 2.75a 3.40a

60% red:60% blue LED 2.73a 3.37a

70% red:30% blue LED 2.74a 3.38a

80% red:20% blue LED 2.93a 3.44a

Natural light - Control 2.90a 3.45a

The values in each column followed by different characters are significantly different (Duncan test, P < 0.05).**: Significant at P ≤ 0.01

The similarities were also found in baby mustard greens (Table 4.4) The combination of red and blue LED treatments always gave the highest number of leaves on plant and equivalent to the control

The combination of red and blue LED light treatments had the effect of increasing the number of leaves on baby radish and mustard greens The same

observation was found in study of Shin et al (2014) on lettuce According to Nguyen

Bao Ve and Nguyen Huy Tai (2010), leaves were the main photosynthetic organs and range between 90-95% of crop productivity was due to photosynthesis, the more leaves plants had, the better photosynthetic efficiency contributed greatly

c Commercial productivity

The commercial yield of baby radish greens under combination of red and blue LED treatments (2.00-2.06 kg/m2) was equivalent to natural light (2.08 kg/m2) (Figure 4.3) The combination of red and blue LED had a good effect on the commercial yield of baby radish greens The same observation was found in the

study of Yorio et al (2001) and Zhang et al (2017) The commercial yield under

red LED (2.00 kg/m2) also reached a control equivalent, although the total yield in this treatment was significantly lower than

Figure 4.3 Productivity of baby radish greens affected by the LED spectrum at 19

DAS This can be explained by the fact that under red monochromatic light, baby

radishes grew the height but gave fewer leaves and smaller size (Figure 4.4)

Therefore, the leaves below were less obscured and retained ventilation on the ground, so the non-commercial part was less than the treatments that grew strongly

in number and size of leaves Blue LED and white LED provided the lowest commercial productivity

LED light spectrum

Total productivity Commercial productivity

Figure 4.4 Baby radish greens under 7 LED spectrum at 19 DAS (a) red LED, (b)

blue LED, (c) white LED, (d) 50% red:50% blue LED, (e) 60% red:40% blue LED, (f) 70% red:30% blue LED, (g) 80% red:20% blue LED and (h) natural light

The different effect of LED light spectra on commercial productivity was also found on baby mustard greens (Figure 4.2) Commercial yield of baby mustard greens under 80% red: 20% blue LED and red LED was insignificantly difference from control This was explained in the same way as on baby radish greens Under natural light, the number and size of baby mustard greens leaves grew rapidly so that the leaves below were obscured, led to increase the non-commercial parts

Figure 4.5 Productivity of baby mustard greens affected by the LED spectrum

at harvest time – 19 DAS

In summary, the growth and yield of baby greens under 80% red: 20% blue LED resulted higher than the other spectral treatments Therefore, this LED spectra was chosen to research on LED light intensities and photoperiods in the second content

(c) (b)

(g) (f)